Feedlot cattle more than double in weight in under 200 days. Beef cattle are slaughtered at under 24 months. How could 93% of a feedlot animal's diet be grazed grass?
The numbers there show the percentage of potentially human palatable food that is consumed by cattle, namely corn.
As the article points out, byproducts such as alcohol production waste are used in feedlot feed. This very much does not mean that a high percentage of feed is grazed grass.
If you have ever made the mistake of trying to eat feed corn, you know that the real world amount of human palatable food fed to cattle is about zero. But that does not matter.
The reason it does not matter is that the land, fuel, water, and capital equipment that goes into making feed for cattle is still entailed in feeding cattle, for about half the weight of each steer.
Tl;dr: the article is not apropos.
EDIT: I should clarify that I do not mean that feed amounts to half the weight of the steer. It takes 6kg of feed to add 1kg to the weight of a steer. Feedlot cows consume about three times in feed what they weigh on the way to slaughter.
